Mixture of titanyltetraazaporphyrin compounds and electrophotographic photoconductor using the same

ABSTRACT

A mixture is made of a plurality of different titanyltetraazaporphyrin compounds, each of which is represented by formula (1):  
                 
 
     wherein A, B, C and D are each independently an unsubstituted or substituted benzene ring or pyridine ring, a substituent thereof being selected from the group consisting of nitro group, cyano group, a halogen atom, an alkyl group having 1 to 8 carbon atoms, an alkoxyl group having 1 to a carbon atoms, and an aryl group. The above-mentioned mixture is contained in a photoconductive layer of an electrophotographic photoconductor as a photoconductive material.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a mixture of a plurality ofdifferent titanyltetraazaporphyrin compounds, and an electrophotographicphotoconductor comprising a photoconductive layer in which theabove-mentioned mixture of the titanyltetraazaporphyrin compounds iscontained as the photoconductive material.

[0003] 2. Discussion of Background

[0004] Conventionally, the photoconductive material for use in theelectrophotographic process is roughly divided into two groups, that is,an inorganic photoconductive material and an organic photoconductivematerial. The above-mentioned electrophotographic process is one of theimage forming processes, through which the surface of the photoconductoris charged uniformly in the dark to a predetermined polarity, forinstance, by corona charge. The uniformly charged photoconductor isexposed to a light image to selectively dissipate the electric charge ofthe exposed area, so that a latent electrostatic image is formed on thephotoconductor. The thus formed latent electrostatic image is developedinto a visible image by use of a toner comprising a coloring agent suchas a dye or pigment, and a polymeric material. Such anelectrophotographic process is called “Carlson process”.

[0005] The photoconductor employing the organic photoconductive materialis advantageous over that employing the inorganic photoconductivematerial with respect to the degree of freedom in the wave range of thelight to be employed, and the film-forming properties, flexibility,transparency, productivity, toxicity, and manufacturing cost of thephotoconductor. In light of the above-mentioned advantages, most of thecurrent photoconductors employ the organic photoconductive material.

[0006] The photoconductor which is repeatedly operated by theabove-mentioned electrophotographic process or the like is required toexhibit excellent electrostatic properties, more specifically, excellentphotosensitivity, acceptance potential, retentivity of charge, potentialstability, residual potential, and spectral sensitivity.

[0007] In recent years, the development of data processing apparatusemploying the above-mentioned electrophotographic process is remarkable.In particular, there is a remarkable improvement in the printing qualityand the reliability of the digital printer which is capable of recordingdata by digital recording method, to be more specific, converting thedata into digital signals and recording the data using a light. Such adigital recording system is applied not only to the printer, but also tothe copying machine. Thus, the digital copying machine is activelydeveloped. It is supposed that the demand for the digital copyingmachine will further increase in line with the addition of various dataprocessing functions.

[0008] The photoconductor designed for the above-mentioned digitalrecording system is required to have special characteristics which aredifferent from those required for the conventional analogue recordingsystem. For instance, semiconductor laser (LD) or light emitting diode(LED) is widely employed as a light source for the digital recordingsystem because of its compactness, cheapness and high reliability. Thewave range of the currently used Lo is within the near infrared region,and the wavelength of the currently used LED is 650 nm or more.Therefore, the electrophotographic photoconductors for use with theabove-mentioned digital recording system are required to show sufficientsensitivity in the wavelength range from the visible region to the nearinfrared region.

[0009] In light of the above-mentioned sensitivity, a squarylium dye(Japanese Laid-Open Patent Applications 49-105536 and 58-21416), atriphenylamine trisazo pigment (Japanese Laid-Open Patent Application61-151659), and a phthalocyanine pigment (Japanese Laid-Open PatentApplications 48-34189 and 57-14874) are proposed as the photoconductivematerials for use in the digital recording.

[0010] In particular, the phthalocyanine pigment, that is, atitanyltetraazaporphyrin compound, can show absorption andphotosensitivity in the relatively long wavelength range. In addition, avariety of phthalocyanine pigments can be obtained according to the kindof central metal or the type of crystalline form. Therefore, researchand development of this type of phthalocyanine pigment has been activelyconducted to obtain the improved photoconductive material for use withthe digital recording.

[0011] Examples of the conventional phthalocyanine pigments capable ofshowing good sensitivity include E -type copper phthalocyanine, K-typemetal-free phthalocyanine, r-type metal-free phthalocyanine, vanadylphthalocyanine, and titanyl phthalocyanine.

[0012] To be more specific, titanylphthalocyanine pigments with highsensitivity are proposed in Japanese Laid-Open Patent Applications64-17066, 3-128973 and 5-98182. Those titanylphthalocyanine pigmentsexhibit maximum absorption in the wavelength range of 700 to 860 nm, sothat they can show remarkably high sensitivity with respect to thesemiconductor laser beam. However, when each of the above-mentionedtitanylphthalocyanine pigments is employed in the electrophotographicphotoconductor, there still remain a lot of practical problems, forexample, decline in charging performance due to fatigue, andtemperature- and humidity-dependence of the charging characteristicsalthough the sensitivity is sufficient. This is reported in Y. Fujimaki,Proc. IS&Ts 7th International Congress on Advances in Non-ImpactPrinting Technologies, 1,269 (1991); K. Daimon et al.; J. Imaging Sci.Technol., 40,249 (1996).

[0013] Japanese Patent Nos. 2637487 and 2637485 disclosetetraazaporphyrin pigments having a heterocycle such as pyridine orpyrazine. Further, Japanese Patent Publication No. 3-27111 and JapanesePatent No. 2754739 discloses that a mixture of a phthalocyanine pigmentand a pyridinoporphyradine pigment is effective as the photoconductivematerial.

[0014] In addition, a mixture of copper-tetraazaporphyrin compoundsobtained by allowing pyridine-3,4-dicarboxylic acid to react withphthalic anhydride is disclosed in Japanese Patent Publication No.3-27111.

[0015] Even though those photoconductive materials are employed in theelectrophotographic photoconductor, the above-mentioned requirements forthe photoconductor are not satisfied. Namely, the sensitivity in thevisible light range and the near infrared range, and the chargingcharacteristics are still unsatisfactory, and in particular, thedurability of the photoconductor is insufficient when the photoconductoris subjected to repeated electrophotographic operations.

SUMMARY OF THE INVENTION

[0016] Accordingly, it is a first object to provide an organicphotoconductive material for use in the electrophotographicphotoconductor, free of the shortcomings of the conventionalphotoconductive materials, capable of exhibiting high sensitivity withrespect to light from the visible light range to the near infraredrange, excellent charging characteristics, and stable electrostaticcharacteristics in the fatigue properties.

[0017] A second object of the present invention is to provide a methodof producing the above-mentioned photoconductive material.

[0018] A third object of the present invention is to provide anelectrophotographic photoconductor employing the above-mentionedphotoconductive material.

[0019] A fourth object of the present invention is to provide an imageforming apparatus comprising the above-mentioned photoconductor.

[0020] The first object of the present invention can be achieved by amixture of a plurality of different titanyltetraazaporphyrin compounds,each of which is represented by formula (1):

[0021] wherein A, B, C and D are each independently an unsubstituted orsubstituted benzene ring or pyridine ring, a substituent thereof beingselected from the group consisting of nitro group, cyano group, ahalogen atom, an alkyl group having 1 to 8 carbon atoms, an alkoxylgroup having 1 to 8 carbon atoms, and an aryl group.

[0022] It is preferable that the above-mentioned mixture oftitanyltetraazaporphyrin compounds exhibit peaks at 576, 577, 579, 579and 580 when subjected to mass spectrometric analysis.

[0023] Further, it is preferable that the above-mentioned mixturecomprise (a) a titanyltetraazaporphyrin compound with formula (1) inwhich A, B, C and D are each an unsubstituted benzene ring, (b) atitanyltetraazaporphyrin compound with formula (1) in which three of A,B, C and D are each an unsubstituted benzene ring and the rest thereofis an unsubstituted pyridine ring, (c) a titanyltetraazaporphyrincompound with formula (1) in which two of A, B, C and D are each anunsubstituted benzene ring and the rest thereof are each anunsubstituted pyridine ring, (d) a titanyltetraazaporphyrin compoundwith formula (1) in which one of A, B, C or D is an unsubstitutedbenzene ring, and the rest thereof are each an unsubstituted pyridinering, and (e) a titanyltetraazaporphyrin compound with formula (1) inwhich A, B, C and D are each an unsubstituted pyridine ring.

[0024] Furthermore, it is preferable that the mixture exhibit at leastone of diffraction peaks at 6.9°, 26.2°, 27.2° and 28.5° in terms of aBragg angle of 2θ±0.2° in an X-ray diffraction spectrum using a Cu-Kαray with a wavelength of 1.54 Å.

[0025] The mixture of titanyltetraazaporphyrin compounds may be producedby allowing phthalonitrile, dicyanopyridine, and a titanium compound toreact.

[0026] The second object of the present invention can be achieved by amethod of producing at least one mixture of a plurality of differenttitanyltetraazaporphyrin compounds, each of whichtitanyltetraazaporphyrin compounds is represented by the above-mentionedformula (1), comprising the step of allowing phthalonitrile,dicyanopyridine, and a titanium compound to react.

[0027] In the above-mentioned preparation method, at least two of themixtures which are different may be produced and mixed, each of thedifferent mixtures being produced by mixing the phthalonitrile and thedicyanopyridine at a different mixing ratio.

[0028] In the above-mentioned preparation method, a phthalocyaninepigment may be added to the mixture when the phthalonitrile and thedicyanopyridine are mixed.

[0029] In addition, it is preferable that the preparation method furthercomprise the step of subjecting the mixture to crystal modificationtreatment.

[0030] The third object of the present invention can be achieved by anelectrophotographic photoconductor which comprises an electroconductivesupport and a photoconductive layer formed thereon comprising a mixtureof a plurality of different titanyltetraazaporphyrin compounds, each ofwhich is represented by the above-mentioned formula (1).

[0031] The fourth object of the present invention can be achieved by animage forming apparatus comprising an electrophotographic photoconductorwhich comprises an electroconductive support and a photoconductive layerformed thereon comprising a mixture of a plurality of differenttitanyltetraazaporphyrin compounds, each of which is represented by theabove-mentioned formula (1)

BRIEF DESCRIPTION OF THE DRAWINGS

[0032] A more complete appreciation of the invention and many of theattendant advantages thereof will be readily obtained as the samebecomes better understood by reference to the following detaileddescription when considered in connection with the accompanyingdrawings, wherein:

[0033]FIG. 1 is an X-ray diffraction spectrum of a mixture (No. 1) oftitanyltetraazaporphyrin compounds in the form of a powder obtained inExample 1-1.

[0034]FIG. 2 is an X-ray diffraction spectrum of a mixture oftitanyltetraazaporphyrin compounds in the form of a powder obtained bysubjecting the mixture No. 1 to acid treatment in Example 1-8.

[0035]FIG. 3 is an X-ray diffraction spectrum of a mixture (No. B) oftitanyltetraazaporphyrin compounds in the form of a powder obtained inExample 1-8.

[0036]FIG. 4 is an X-ray diffraction spectrum of a mixture (No. 15) oftitanyltetraazaporphyrin compounds in the form of a powder obtained inExample 1-15.

[0037]FIG. 5 is an X-ray diffraction spectrum of a mixture (No. 16) oftitanyltetraazaporphyrin compounds in the form of a powder obtained inExample 1-16.

[0038]FIG. 6 is an X-ray diffraction spectrum of a mixture (No. 19) oftitanyltetraazaporphyrin compounds in the form of a powder obtained inExample 1-19.

[0039]FIG. 7 is an X-ray diffraction spectrum of a Y-typetitanylphthalocyanine in the form of a powder employed in anelectrophotographic photoconductor fabricated in Comparative Example2-3.

[0040]FIG. 8 is a chart showing the change in surface potential of theelectrophotographic photoconductors obtained in Example 2-1 andComparative Example 2-3 in the fatigue test.

[0041]FIG. 9 is an X-ray diffraction spectrum of a mixture ofcopper-tetraazaporphyrin compounds in the form of a powder obtained inComparative Example 1-3.

[0042]FIG. 10 is a chart showing the results of mass spectrometricanalysis of a mixture (No. 1) of titanyltetraazaporphyrin compoundsobtained in Example 1-1.

[0043]FIG. 11 is a chart showing the results of mass spectrometricanalysis of a titanyltetrapyridoazaporphyrin compound (comparativecompound No. 1) obtained in Comparative Example 1-1.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0044] In the mixture of a plurality of differenttitanyltetraazaporphyrin compounds according to the present invention,each titanyltetraazaporphyrin compound is represented by formula (1):

[0045] wherein A, B, C and D are each independently an unsubstituted orsubstituted benzene ring or pyridine ring, a substituent thereof beingselected from the group consisting of cyano group, a halogen atom, analkyl group having 1 to 8 carbon atoms, an alkoxyl group having 1 to 8carbon atoms, and an aryl group.

[0046] The above-mentioned mixture, which is novel, can be conveniently,reproducibly and surely obtained in high yield according to thepreparation method of the present invention.

[0047] A plurality of different titanyltetraazaporphyrin compounds inthe mixture of the present invention can be confirmed and analyzed, forexample, by mass spectrometric analysis. Namely, by observing thefragment peaks of molecular weight, each titanyltetraazaporphyrincompound corresponding to the molecular weight can be identified.

[0048] The sensitivity of the electrophotographic photoconductor whichcontains such a mixture of the titanyltetraazaporphyrin compounds asspecified in the present invention becomes better than that of thephotoconductor which employs a mixture of tetraazaporphyrin compoundshaving other center metals than titanium. Understandably therefore,titanium as the center metal is considered to contribute to theimprovement of sensitivity. Further, when the electrophotographicphotoconductor comprises a mixture of the titanyltetraazaporphyrincompounds according to the present invention, the electrostaticstability of the photoconductor after repeated electrophotographicoperations is superior to that of the photoconductor employing theconventional titanyl phthalocyanine pigment. The use of a plurality oftitanyltetraazaporphyrin compounds in the form of a mixture is supposedto be beneficial to the electrostatic stability.

[0049] In the aforementioned formula (1), A, B, C and D are each abenzene ring which may have a substituent, or a pyridine ring which mayhave a substituent.

[0050] Examples of the substituent for the benzene ring or pyridine ringinclude nitro group, cyano group, a halogen atom, an alkyl group whichmay have a substituent, an alkoxyl group which may have a substituent,and an aryl group which may have a substituent.

[0051] Specific examples of the above-mentioned halogen atom serving asthe substituent are iodine atom, bromine atom, chlorine atom, andfluorine atom.

[0052] Specific examples of the above-mentioned alkyl group serving asthe substituent include methyl group, ethyl group, n-propyl group,iso-propyl group, tert-butyl group, sec-butyl group, n-butyl group,iso-butyl group, trifluoromethyl group, 2-cyancethyl group, benzylgroup, 4-chlorobenzyl group, and 4-methylbenzyl group.

[0053] Specific examples of the above-mentioned alkoxyl group serving asthe substituent include methoxy group, ethoxy group, n-propoxy group,iso-propoxy group, n-butoxy group, iso-butoxy group, sec-butoxy group,tert-butoxy group, 2-hydroxyethoxy group, 2-cyanoethoxy group, benzyloxygroup, 4-methylbenzyloxy group, and trifluoromethoxy group.

[0054] Specific examples of the above-mentioned aryl group serving asthe substituent include phenyl group, naphthyl group, biphenylyl group,terphenylyl group, pyrenyl group, fluorenyl group,9,9-dimethyl-2-fluorenyl group, azulenyl group, anthryl group,triphenylenyl group, chrysenyl group, fluorenylidenephenyl group,5H-dibenzo[a,d]cycloheptenylidenephenyl group, thienyl group,benzothienyl group, furyl group, benzofuranyl group, carbazolyl group,pyridyl group, pyridinyl group, pyrrolidyl group and oxazolyl group.

[0055] The aryl group may have a substituent such as the same alkylgroup, alkoxyl group and halogen atom as previously mentioned. Further,the aryl group may form a fused ring together with the ring of A, B, Cor D.

[0056] The mixture of titanyltetraazaporphyrin compounds, each of whichis represented by the above-mentioned formula (1), can be obtained, forexample, by allowing a mixture of phthalonitrile of formula (2) anddicyanopyridine of formula (3) or (4), which are shown below, to reactwith a titanium compound such as titanium tetrachloride or tetra-n-butylo-titanate. This reaction may be carried out with no solvent, or in asolvent such as α-chloronaphthalene, dichlorobenzene, trichlorobenzene,pentanol, octanol, benzyl alcohol, N,N-dimethylformamide,N-methylpyrrolidone, quinoline, benzene, toluene, xylene, mesitylene,nitrobenzene or dioxane.

[0057] Further, this reaction may be carried out in the presence ofurea, formamide, acetcamide, benzamide,1,8-diazabicyclo[5,4,0]-7-undecene (DBU), or ammonia.

[0058] The reaction temperature is commonly set wihin the range fromroom temperature to 300° C., preferably 100 to 250° C.

[0059] For convenience, both the phthalonitrile of formula (2) and thedicyanopyridine of formula (3) or (4) have no substituent. Both may havesuch a substituent as mentioned above.

[0060] The phthalonitrile as the starting material, represented byformula (2), may be replaced by the compounds of formulas (5) to (7),while the dicyanopyridine as the starting material, represented byformula (3) or (4), may be replaced by the compounds of formulas (8) to(13) In this case, the mixture of the titanyltetraazaporphyrin compoundsof formula (1) can be produced in a similar manner as mentioned above.

[0061] In the synthesis of the mixture of the titanyltetraazaporphyrincompounds, it is preferable that the molar ratio of the phthalonitrileof formula (2) to the dicyanopyridine of formula (3) or (4) be in therange of (1:99999) to (99999:1), more preferably in the range of (1:1)to (399:1). When the molar ratio of the phthalonitrile is less than theabove-mentioned lower limit, the charging characteristics and thesensitivity of the obtained photoconductor tend to decrease. When themolar ratio of the dicyanopyridine is less than the above-mentionedlower limit, the decrease of chargeability due to fatigue becomes largeafter the repeated charging and light exposure.

[0062] In response to the requirements for the photoconductor, two ormore different mixtures of the titanyltetraazaporphyrin compounds may beproduced and mixed, each of the different mixtures being produced bymixing the phthalonitrile and the dicyanopyridine at a different mixingratio.

[0063] Furthermore, a phthalocyanine pigment may be added to the mixturewhen the phthalonitrile and the dicyanopyridine are mixed.

[0064] Examples of the phthalocyanine pigment for use in the presentinvention include copper phthalocyanine, metal-free phthalocyanine,aluminum phthalocyanine, magnesium phthalocyanine, chlorogalliumphthalocyanine, hydroxygallium phthalocyanine, vanadyl phthalocyanine,titanyl phthalocyanine, chloroindium phthalocyanine, hydroxyindiumphthalocyanine, zinc phthalocyanine, iron phthalocyanine, and cobaltphthalocyanine.

[0065] It is preferable that the mixture of a plurality of differenttitanyltetraazaporphyrin compounds of the present invention be in acrystalline state, in particular, be in such a specific crystalline formthat exhibits at least a diffraction peak at 6.9°, 26.2°, 27.2° or 28.5°in terms of a Bragg angle 2θ±0.2° in an X-ray diffraction spectrum usinga Cu-Kα ray (λ=1.54 Å).

[0066] The above-mentioned preparation method of the mixtureof-titanyltetraazaporphyrin compounds makes it possible to obtain themixture in a crystalline state. Further, a desired crystalline form maybe obtained by subjecting the mixture to crystal modification treatment.

[0067] To be more specific, acid treatment, solvent treatment,mechanical treatment, and heating treatment are available as the crystalmodification treatment methods of a mixture of thetitanyltetraazaporphyrin compounds.

[0068] The acid treatment is carried out in such a manner that themixture of titanyltetraazaporphyrin compounds is first dissolved in anacid such as trichloroacetic acid or trifluoroacetic acid at atemperature ranging from 0° C. to room temperature. The thus preparedsolution is added dropwise to ice-cold water or an organic solvent inwhich the mixture of the titanyltetraazaporphyrin compounds is slightlysoluble to precipitate the crystals of the mixture. The precipitatedcrystals are collected, for example, by filtration.

[0069] In the treatment using a solvent, the mixture of thetitanyltetraazaporphyrin compounds is suspended in a solvent withstirring at room temperature or under the application of heat.

[0070] The previously mentioned mechanical treatment means millingtreatment by use of, for example, automatic mortar, planetary mill, ballmill, oscillating ball mill, kneader, attritor, or sand mill. Themilling treatment is performed at room temperature or under theapplication of heat, using milling media such as glass beads, steelbeads, alumina balls, PSZ balls, YTZ balls, salt, and Glauber's salt.The mixture of the titanyltetraazaporphyrin compounds may be subjectedto milling using the above-mentioned media in a solvent.

[0071] The heating treatment is carried out in combination with theabove-mentioned acid treatment, solvent treatment, or mechanicaltreatment. In addition, the crystals of the mixture of thetitanyltetraazaporphyrin compounds may be directly heated at atemperature higher than the crystalline transition temperature using anelectric furnace in the atmosphere or in the presence of an inert gas.

[0072] Specific examples of the solvent used in the above-mentionedtreatment include aromatic solvents such as benzene, toluene,dichlorobenzene, and nitrobenzene; alcohols such as methanol, ethanol,and benzyl alcohol; ketones such as acetone, cyclohexanone, and methylethyl ketone; ethers such as n-butyl ether, ethylene glycol n-butylether, and tetrahydrofuran; amines such as N,N-dimethylformamide, andN-methylpyrrolidone; basic solvents such as quinoline and pyridine;dimethyl sulfoxide; and water.

[0073] A plurality of different titanyltetraazaporphyrin compounds inthe mixture can be confirmed and analyzed, for example, by massspectrometric analysis. Namely, by confirming the presence of a fragmentpeak corresponding to the molecular weight of eachtitanyltetraazaporphyrin compound, the titanyltetraazaporphyrin compoundcan be identified.

[0074] An electrophotographic photoconductor of a single-layered type ora layered type (function-separating type) can be fabricated, using asthe photoconductive material the mixture of titanyltetraazaporphyrincompounds according to the present invention alone, or in combinationwith a charge transport material.

[0075] To fabricate the electrophotographic photoconductor of asingle-layered type, a photoconductive layer is provided on anelectroconductive support in such a manner that a mixture oftitanyltetraazaporphyrin compounds is singly dispersed in a binder resinor together with a charge transport material, and the thus prepareddispersion is coated on the support.

[0076] In the case where the electrophotographic photoconductor of alayered type (function-separating type) is fabricated, a chargegeneration layer comprising a mixture of titanyltetraazaporphyrincompounds is provided on an electroconductive support, and a chargetransport layer comprising a charge transport material is overlaid onthe charge generation layer. The above-mentioned overlaying order of thecharge generation layer, and the charge transport layer may be reversed.

[0077] The electrophotographic photoconductor of the present inventionmay further comprise an intermediate layer which is provided between theelectroconductive support and the photoconductive layer in order toimprove the adhesion between the support and the photoconductive layer,and enhance the charge blocking characteristics.

[0078] Furthermore, a protective layer may be provided on thephotoconductive layer to improve the wear resistance and the mechanicaldurability of the photoconductor.

[0079] To form the photoconductive layer in which a mixture oftitanyltetraazaporphyrin compounds is dispersed, the mixture oftitanyltetraazaporphyrin compounds, and a binder resin optionally addedthereto, are dispersed or dissolved in an appropriate solvent, using aball mill, ultrasonic wave, or a homomixer. Then, the above preparedcoating liquid may be coated on the electroconductive support by dipcoating, blade coating or spray coating.

[0080] To upgrade the dispersibility of the mixture oftitanyltetraazaporphyrin compounds in the photoconductive layer, it ispreferable that the average particle size of the mixture oftitanyltetraazaporphyrin compounds be 2 μm or less, more preferably 1 μmor less. Further, the lower limit of the average particle size may beset at 0.01 μm so as to inhibit the aggregation of fine particles. Thus,the increase of the resistivity of the photoconductive layer can beprevented, and the deterioration of sensitivity and durability due tothe increase of defective crystallites can be prevented in the repeateduse.

[0081] Specific examples of the solvent which is used to prepare adispersion or solution for the formation of the photoconductive layerinclude N,N-dimethylformamide, toluene, xylene, monochlorobenzene,1,2-dichloroethane, 1,1,1-trichloroethane, dichloromethane,1,1,2-trichloroethane, trichlorcethylene, tetrahydrofuran, methyl ethylketone, methyl isobutyl ketone, cyclohexanone, ethyl acetate, and butylacetate.

[0082] Any binder resin that has good electrically insulating propertiesand conventionally used in the preparation of the electrophotographicphotoconductor can be employed for the formation of the photoconductivelayer in the present invention.

[0083] Specific examples of such a binder resin include additionpolymerization-type resins, polyaddition-type resins andpolycondensation-type resins such as polyethylene, polyvinyl butyral,polyvinyl formal, polystyrene resin, phenoxy resin, polypropylene,acrylic resin, methacrylic resin, vinyl chloride resin, vinyl acetateresin, epoxy resin, polyurethane resin, phenolic resin, polyester resin,alkyd resin, polycarbonate resin, polyamide resin, silicone resin andmelamine resin; copolymer resins comprising as the repeat units two ormore monomers for use in the above-mentioned resins, for example,electrically insulating resins such as vinyl chloride-vinyl acetatecopolymer resin, styrene-acrylic copolymer resin, and vinylchloride-vinyl acetate-maleic anhydride copolymer resin; and a polymericorganic semiconductor such as poly-N-vinylcarbazole. Those binder resinsmay be used alone or in combination.

[0084] The mixture of titanyltetraazaporphyrin compounds according tothe present invention may be used in combination with the followingpigments: organic pigments, for example, azo pigments such as C.I.Pigment Blue 25 (C.I. 21180), C.I. Pigment Red 41 (C.I. 21200), C.I.Acid Red 52 (C.I. 45100), C.I. Basic Red 3 (C.I. 45210), an azo pigmenthaving a carbazole skeleton (Japanese Laid-Open Patent Application53-95033), an azo pigment having a distyryl benzene skeleton (JapaneseLaid-Open Patent Application 53-133445), an azo pigment having atriphenylamine skeleton (Japanese Laid-Open Patent ApplicationS3-132347), an azo pigment having a dibenzothiophene skeleton (JapaneseLaid-Open Patent Application 54-21728), an azo pigment having anoxadiazole skeleton (Japanese Laid-Open Patent Application 54-12742), anazo pigment having a fluorenone skeleton (Japanese Laid-Open PatentApplication 54-22834), an azo pigment having a bisstilbene skeleton(Japanese Laid-Open Patent Application 54-17733), an azo pigment havinga distyryl oxadiazole skeleton (Japanese Laid-Open Patent Application54-2129), and an azo pigment having a distyryl carbazole skeleton(Japanese Laid-Open Patent Application 54-14967); phthalocyaninepigments such as C.I. Pigment Blue 16 (C.I. 74100) and titanylphthalocyanine; indigo pigments such as C.I. Vat Brown 5 (C.I. 73410)and C.I. Vat Dye (C.I. 73030); and perylene pigments such as AlgolScarlet 3 and Indanthrene Scarlet R (made by Bayer Co., Ltd.). Two ormore organic pigments mentioned above may be used in combination withthe mixture of titanyltetraazaporphyrin compounds of formula (1).

[0085] In the layered photoconductor in which the charge generationlayer and the charge transport layer are successively overlaid on theelectroconductive support in this order, it is preferable that theamount of the mixture of titanyltetraazaporphyrin compounds in thecharge generation layer be in the range of 20 to 900 wt % of the entireweight of the binder resin for use in the charge generation layer. Thethickness of the above-mentioned charge generation layer is preferablyin the range of 0.01 to 5 μm. Further, in this case, it is preferablethat the amount of the charge transport material in the charge transportlayer be in the range of 20 to 200 wt % of the entire weight of thebinder resin for use in the charge transport layer. The thickness of thecharge transport layer is preferably in the range of 5 to 100 μm. Thecharge transport layer may be formed using a high-molecular weightcharge transport material alone.

[0086] Further, in such a case, the addition of-the charge transportmaterial to the charge generation layer is effective for reducing theresidual potential and improving the photosensitivity. When the chargetransport material is added to the charge generation layer, as mentionedabove, it is preferable that the amount of charge transport material bein the range of 20 to 200 wt % of the total weight of the binder resinfor use in the charge generation layer.

[0087] In the single-layered photoconductive layer, it is preferablethat the amount of the mixture of titanyltetraazaporphyrin compounds bein the range of 5 to 95 wt % of the entire weight of the binder resinfor use in the photoconductive layer. In this case, the thickness of thesingle-layered photoconductive layer is preferably in the range of 10 to100 μm. When a charge transport material is adder to the single-layeredphotoconductive layer, it is preferable that the amount of the chargetransport material be in the range of 30 to 200 wt % of the entireweight of the binder resin for use in the single-layered photoconductivelayer.

[0088] There can be employed a photoconductive layer comprising ahigh-molecular weight charge transport material and the mixture oftitanyltetraazaporphyrin compounds according to the present invention.In this case, it is preferable that the amount of the mixture oftitanyltetraazaporphyrin compounds be in the range of 5 to 95 wt % ofthe entire weight of the high-molecular weight charge transportmaterial. In this case, it is preferable that the thickness of thephotoconductive layer be in the range of 10 to 100 μm.

[0089] To improve the chargeability, the photoconductive layer mayfurther comprise a phenol compound, a hydroquinone compound, a hinderedphenol compound, a hindered amine compound, and a compound having ahindered amine and a hindered phenol in a molecule thereof.

[0090] For the electroconductive support, there can be employed ametallic plate, drum or foil made of aluminum, nickel, copper, titanium,gold or stainless steel; a plastic film on which an electroconductivematerial such as aluminum, nickel, copper, titanium, gold, tin oxide orindium oxide is deposited; and a sheet of paper or a plastic film, whichmay be formed in a drum, coated with an electroconductive material.

[0091] The electrophotographic photoconductor of the present inventionmay further comprise an intermediate layer which is provided between theelectroconductive support and the photoconductive layer, as previouslymentioned. The intermediate layer comprises a resin as the maincomponent. The photoconductive layer is provided on the intermediatelayer by coating method using a solvent, so that it is desirable thatthe resin for use in the intermediate layer have high resistance againstgeneral-purpose organic solvents.

[0092] Preferable examples of the resin for use in the intermediatelayer include water-soluble resins such as polyvinyl alcohol, casein andsodium polyacrylate; alcohol-soluble resins such as copolymer nylon andmethoxymethylated nylon; and hardening resins with three-dimensionalnetwork such as polyurethane, melamine resin, phenolic resin,alkyd-melamine resin and epoxy resin.

[0093] The intermediate layer may further comprise finely-dividedparticles of metallic oxides such as titanium oxide, silica, alumina,zirconium oxide, tin oxide and indium oxide in order to prevent theoccurrence of Moire and reduce the residual potential.

[0094] Similar to the previously mentioned photoconductive layer, theintermediate layer can be provided on the electroconductive support bycoating method, using an appropriate solvent.

[0095] Further, the intermediate layer for use in the present inventionmay be prepared using a coupling agent such as a silane coupling agent,titanium coupling agent or chromium coupling agent. Furthermore, toprepare the intermediate layer, Al₂O₃ may be deposited on theelectroconductive support by anodizing process, or an organic materialsuch as poly-para-xylylene (parylene), or an inorganic material such asSiO₂, SnO₂, TiO₂, ITO or CeO₂ ray be deposited on the electroconductivesupport by vacuum thin-film forming method.

[0096] It is proper that the thickness of the intermediate layer be 5 μmor less.

[0097] The electrophotographic photoconductor according to the presentinvention may further comprise a protective layer which is provided onthe photoconductive layer, as previously mentioned.

[0098] The protective layer for use in the present invention comprises aresin. Examples of such a resin for use in the protective layer includeABS resin, ACS resin, copolymer of olefin and vinyl monomer, chlorinatedpolyether, allyl resin, phenolic resin, polyacetal, polyamide,polyamideimide, polyacrylate, polyallyl sulfone, polybutylene,polybutylene terephthalate, polycarbonate, polyether sulfone,polyethylene, polyethylene terephthalate, polyimide, acrylic resin,polymethylpentene, polypropylene, polyphenylene oxide, polysulfone,polystyrene, AS resin, butadiene-styrene copolymer, polyurethane,polyvinyl chloride, polyvinylidene chloride and epoxy resin.

[0099] The protective layer may further comprise a fluorine-containingresin such as polytetrafluoroethylene, and a silicone resin to improvethe abrasion resistance. In addition, inorganic materials such astitanium oxide, tin oxide and potassium titanate may be dispersed in theabove-mentioned fluorine-containing resin and silicone resin.

[0100] The protective layer may be provided on the photoconductive layerby the conventional coating method.

[0101] The thickness of the protective layer is preferably in the rangeof about 0.1 to 10 μm. Furthermore, a vacuum-deposited thin film of a-Cor a-SiC may be used as the protective layer in the present invention.

[0102] The charge transport material for use in the photoconductivelayer include a positive hole transport material and an electrontransport material.

[0103] There can be employed any conventional positive hole transportmaterials, for example, poly-N-carbazole and derivatives thereof,poly-γ-carbazolyl ethylglutamate and derivatives thereof, a condensationproduct of pyrene and formaldehyde and derivatives thereof, polyvinylpyrene, polyvinyl phenanthrene, oxazole derivatives, imidazolederivatives, triphenylamine derivatives, and the following compounds (A)to (R).

[0104] Compound (A) Described in Japanese Laid-Open Patent ApplicationsNos. 55-154955 and 55-156954:

[0105] wherein R¹ is methyl group, ethyl group, 2-hydroxyethyl group, or2-chloroethyl group; R² is methyl group, ethyl group, benzyl group, orphenyl group; and R³ is a hydrogen atom, a chlorine atom, a bromineatom, an alkyl group having 1 to 4 carbon atoms, an alkoxyl group having1 to 4 carbon atoms, a dialkylamino group, or nitro group.

[0106] Examples of the above compound of formula (A) are9-ethylcarbazole-3-aldehyde-1-methyl-1-phenylhydrazone,9-ethylcarbazole-3-aldehyde-1-benzyl-1-phenylhydrazone, and9-ethylcarbazole-3-aldehyde-1,1-diphenylhydrazone.

[0107] Compound (B) Described in Japanese Laid-Open Patent ApplicationNo. 55-52063:

[0108] wherein Ar is a naphthalene ring, anthracene ring or styryl ring,each of which may have a substituent, a pyridine ring, furan ring, orthiophene ring; and R is an alkyl group or benzyl group.

[0109] Examples of the above compound of formula (B) are4-diethylaminostyryl-3-aldehyde-1-methyl-1-phenylhydrazone, and4-methoxynaphthalene-1-aldehyde-1-benzyl-1-phenylhydrazone.

[0110] Compound (C) Described in Japanese Laid-Open Patent ApplicationNo. 56-81850:

[0111] wherein R¹ is an alkyl group, benzyl group, phenyl group ornaphthyl group; R² is a hydrogen atom, an alkyl group having 1 to 3carbon atoms, an alkoxyl group having 1 to 3 carbon atoms, adialkylamino group, a diaralkylamino group, or a diarylamino group; n isan integer of 1 to 4, and when n is 2 or more, R² may be the same ordifferent; and R³ is a hydrogen atom or methoxy group.

[0112] Examples of t he above compound of formula (C) are4-methoxybenzaldehyde-1-methyl-1-phenylhydrazone,2,4-dimethoxybenzaldehyde-1-benzyl-1-phenylhydrazone,4-diethylaminobenzaldehyde-1,1-diphenyahydrazone,4-methoxybenzaldehyde-1-benzyl-1-(4-methoxy)phenyl hydrazone,4-diphenylaminobenzaldehyde-1-benzyl-1-phenylhydrazone, and4-dibenzylaminobenzaldehyde-1,1-diphenylhydrazone.

[0113] Compound (D) Described in Japanese Laid-Open Patent ApplicationNo. 51-10983:

[0114] wherein R¹ is an alkyl group having 1 to 11 carbon atoms, asubstituted or unsubstituted phenyl group, or a heterocyclic group; R²and R³ are each independently a hydrogen atom, an alkyl group having 1to 4 carbon atoms, a hydroxyalkyl group, chloroalkyl group, or asubstituted or unsubstituted aralkyl group, and R² and R³ may form anitrogen-containing heterocyclic ring in combination; and R⁴, which maybe the same or different, each is a hydrogen atom, an alkyl group having1 to 4 carbon atoms, an alkoxyl group, or a halogen atom.

[0115] Examples of the above compound of formula (D) are1,1-bis(4-dibenzylaminophenyl)propane,tris(4-diethylaminophenyl)methane,1,l-bis(4-dibenzylaminophenyl)propane, and2,2′-dimethyl-4,4′-bis(diethylamino)triphenylmethane.

[0116] Compound (E) Described in Japanese Laid-Open Patent ApplicationNo. 51-94829;

[0117] wherein R is a hydrogen atom or a halogen atom; and Ar is asubstituted or unsubstituted phenyl group, naphthyl group, anthrylgroup, or carbazolyl group.

[0118] Examples of the above compound of formula (E) are9-(4-diethylaminostyryl) anthracene, and9-bromo-10-(4-diethylaminostyryl) anthracene.

[0119] Compound (F) Described in Japanese Laid-Open Patent ApplicationNo. 52-128373:

[0120] wherein R¹ is a hydrogen atom, a halogen atom, cyano group, analkoxyl group having 1 to 4 carbon atoms, or an alkyl group having 1 to4 carbon atoms; and Ar is

[0121] in which R² is an alkyl group having 1 to 4 carbon atoms; R³ is ahydrogen atom, a halogen atom, an. alkyl group having 1 to 4 carbonatoms, an alkoxyl group having 1 to 4 carbon atoms, or a dialkylaminogroup; n is an integer of 1 or 2, and when n is 2, R³ may be the same ordifferent; and R⁴ and R⁵ are each a hydrogen atom, a substituted orunsubstituted alkyl group having 1 to 4 carbon atoms, or a substitutedor unsubstituted benzyl group.

[0122] Examples of the above compound of formula (F) are9-(4-dimethylaminobenzylidene)fluorene, and3-(9-fluorenylidene)-9-ethylcarbazole.

[0123] Compound (G) Described in Japanese Laid-Open Patent ApplicationNo. 56-29245:

[0124] wherein R is carbazolyl group, pyridine group, thienyl group,indolyl group, furyl group, a substituted or unsubstituted phenyl group,a substituted or unsubstituted styryl group, a substituted orunsubstituted naphthyl group, or a substituted or unsubstituted anthrylgroup, each of which may have a substituent selected from the groupconsisting of a dialkylamino group, an alkyl group, an alkoxyl group,carboxyl group and an ester group thereof, a halogen atom, cyano group,an aralkylamino group, an N-alkyl-N-aralkylamino group, amino group,nitro group and acetylamino group.

[0125] Examples of the above compound of formula (G) are1,2-bis(4-diethylaminostyryl)benzene, and1,2-bis(2,4-dimethoxystyryl)benzene.

[0126] Compound (H) Described in Japanese Laid-Open Patent ApplicationNo. 58-58552:

[0127] wherein R¹ is a lower alkyl group, a substituted or unsubstitutedphenyl group, or benzyl group; R² and R³ are each a hydrogen atom, alower alkyl group, a lower alkoxyl group, a halogen atom, nitro group,or an amino group which may have as a substituent a lower alkyl group orbenzyl group; and n is an integer of 1 or 2.

[0128] Examples of the above compound of formula (H) are3-styryl-9-ethylcarbazole, and 3-(4-methoxystyryl)-9-ethylcarbazole.

[0129] Compound (I) Described in Japanese Laid-Open Patent ApplicationNo. 57-73075:

[0130] wherein R¹ is a hydrogen atom, an alkyl group, an alkoxyl group,or a halogen atom; R² and R³ are each an alkyl group, a substituted orunsubstituted aralkyl group, or a substituted or unsubstituted arylgroup; R⁴ is a hydrogen atom, or a substituted or unsubstituted phenylgroup; and Ar is a substituted or unsubstituted phenyl group, or asubstituted or unsubstituted naphthyl group.

[0131] Examples of the above compound of formula (I) are4-diphenylaminostilbene, 4-dibenzylaminostilbene,4-ditolylaminostilbene, 1-(4-diphenylaminostyryl)naphthalene, and1-(4-diethylaminostyryl)naphthalene.

[0132] Compound (J) Described in Japanese Laid-Open Patent ApplicationNo. 58-198043:

[0133] wherein n is an integer of 0 or 1; R¹ is a hydrogen atom, analkyl group, or a substituted or unsubstituted phenyl group; Ar¹ is asubstituted or unsubstituted aryl group; R⁵ is a substituted orunsubstituted alkyl group, or a substituted or unsubstituted aryl group;and A is 9-anthryl group, a substituted or unsubstituted carbazolylgroup, or

[0134] in which R² is a hydrogen atom, an alkyl group, an alkoxyl group,a halogen atom, or

[0135] in which R³ and R⁴ are each an alkyl group, a substituted orunsubstituted aralkyl group, or a substituted or unsubstituted arylgroup, and R³ and R⁴ may be the same or different, or form a ring incombination; m is an integer of 0 to 3, and when m is 2 or more, R² maybe the same or different; and when n=0, A and R¹ may form a ring incombination.

[0136] Examples of the above compound of formula (J) are4′-diphenylamino-α-phenylstilbene, and4′-bis(methylphenyl)amino-α-phenylstilbene.

[0137] Compound (K) Described in Japanese Laid-Open Patent ApplicationNo. 49-105537:

[0138] wherein R¹, R² and R³ are each a hydrogen atom, a lower alkylgroup, a lower alkoxyl group, a dialkylamino group, or a halogen atom;and n igs an integer of 0 or 1.

[0139] Examples of the above compound of formula (K) include1-phenyl-3-(4-diethyaminostyryl)-5-(4-diethylaminophenyl)pyrazoline and1-phenyl-3-(4-dimethylaminostyryl)-5-(4-dimethylaminophenyl)pyrazoline.

[0140] Compound (L) described in Japanese Laid-Open Patent ApplicationNo. 52-139066:

[0141] wherein R¹ and R² are each a substituted or unsubstituted alkylgroup, or a substituted or unsubstituted aryl group; and A is asubstituted amino group, a substituted or unsubstituted aryl group, oran allyl group.

[0142] Examples of the above compound of formula (L) are2,5-bis(4-diethylaminophenyl)-1,3,4-oxadiazole,2-N,N-diphenylamino-5-(4-diethylaminophenyl)-1,3,4-oxadiazole, and2-(4-dimethylaminophenyl)-5-(4-diethylaminophenyl)-1,3,4-oxadiazole.

[0143] Compound (M) Described in Japanese Laid-Open Patent ApplicationNo. 52-139065:

[0144] wherein X is a hydrogen atom, a lower alkyl group, or a halogenatom; R is a substituted or unsubstituted alkyl group, or a substitutedor unsubstituted aryl group; and A is a substituted amino group, or asubstituted or unsubstituted aryl group.

[0145] Examples of the above compound of formula (M) are2-N,N-diphenylamino-5-(N-ethylcarbazol-3-yl)-1,3,4-oxadiazole, and2-(4-diethylaminophenyl)-5-(N-ethylcarbazol-3-yl)-1,3,4-oxadiazole.

[0146] Compound (N) Described in Japanese Laid-Open Patent ApplicationNo. 58-32372:

[0147] wherein R¹ is a lower alkyl group, a lower alkoxyl group, or ahalogen atom; n is an integer of 0 to 4; and R² and R³ may be the sameor different, and are each a hydrogen atom, a lower alkyl group, a loweralkoxyl group, or a halogen atom.

[0148] Examples of the benzidine compound represented by formula (N) areN,N′-diphenyl-N,N′-bis(3-methylphenyl)-[1,1′-biphenyl]-4,4′-diamine, and3,3′-dimethyl-N,N,N′,N′-tetrakis(4-methylphenyl)-[1,1′-biphenyl]-4,4′-diamine.

[0149] Compound (O) Described in Japanese Laid-Open Patent ApplicationNo. 2-178669:

[0150] wherein R¹, R³ and R⁴ are each a hydrogen atom, amino group, analkoxyl group, a thioalkoxyl group, an aryloxy group, methylenedioxygroup, a substituted or unsubstituted alkyl group, a halogen atom, or asubstituted or unsubstituted aryl group; R² is a hydrogen atom, analkoxyl group, a substituted or unsubstituted alkyl group, or a halogenatom, provided that R¹, R², R³ and R⁴ are not hydrogen atoms at the sametime; and k, l, m and n are each an integer of 1 to 4, and when each isan integer of 2, 3 or 4, R¹, R², R³ and R⁴ may be independently the sameor different.

[0151] Examples of the biphenylamine compound represented by formula (O)are 4′-methoxy-N,N-diphenyl-[1,1′-biphenyl]-4-amine,4′-methyl-N,N′-bis(4-methylphenyl)-[1,1′-biphenyl]-4-amine, and4′-methoxy-N,N′-bis(4-methylphenyl)-[1,1′-biphenyl]-4-amine,

[0152] Compound (P) Described in Japanese Laid-Open Patent ApplicationNo. 3-285960:

[0153] wherein Ar is a condensed polycyclic hydrocarbon group having 18or less carbon atoms; and R¹ and R² are each a hydrogen atom, a halogenatom, a substituted or unsubstituted alkyl group, an alkoxyl group, or asubstituted or unsubstituted phenyl group, and R¹ and R² may be the sameor different.

[0154] Examples of the triarylamine compound represented by formula (P)are 1-diphenylaminopyrene, and 1-di(p-tolylamino)pyrene.

[0155] Compound (Q) described in Japanese Laid-Open Patent ApplicationNo. 62-98394:

A—CH═CH—Ar—CH═CH—A  (Q)

[0156] wherein Ar is a substituted or unsubstituted aromatic hydrocarbongroup; and A is

[0157] in which Ar′ is a substituted or unsubstituted aromatichydrocarbon group; and R¹ and R² are each a substituted or unsubstitutedalkyl group, or a substituted or unsubstituted aryl group.

[0158] Examples of the diolefin aromatic compound represented by formula(Q) are 1,4-bis(4-diphenylaminostyryl)benzene, and1,4-bis[4-di(p-tolyl)aminostyryl]benzene.

[0159] Compound (R) Described in Japanese Laid-Open Patent ApplicationNo. 4-230764:

[0160] wherein Ar is an aromatic hydrocarbon group; R is a hydrogenatom, a substituted or unsubstituted alkyl group, or a substituted orunsubstituted aryl group; and n is an integer of 0 or 1, and m is aninteger of 1 or 2, and when n=0 and m=1, Ar and R may form a ring incombination.

[0161] Examples of the styrylpyrene compound represented by formula (R)are 1-(4-diphenylamininostyryl)pyrene, and1-[4-di(p-tolyl)aminostyryl]pyrene.

[0162] Examples of the electron transport material for use in thepresent invention are chloroanil, bromoanil, tetracyanoethylene,tetracyanoquinodimethane, 2,4,7-trinitro-9-fluorenone,2,4,5,7-tetranitro-9-fluorenone, 2,4,5,7-tetranitroxanthone,2,4,8-trinitrothioxanthone,2,6,8-trinitro-indeno4H-indeno[1,2-b]thiophen-4-one, and1,3,7-trinitrodibenzothiophene-5,5-dioxide.

[0163] In particular, the following electron transport materials offormulas (S) (T) and (U) are preferably employed because of theirexcellent electron transporting performance.

[0164] The above-mentioned charge transport materials may be used aloneor in combination.

[0165] The mixture of titanyltetraazaporphyrin compounds of formula (1)according to the present invention is useful as the photoconductivematerial for use in the electrophotographic photoconductor, and inaddition, as the electronic device in the solar battery and the opticaldisk in the field of electronics.

[0166] Other features of this invention will become apparent in thecourse of the following description of exemplary embodiments, which aregiven for illustration of the invention and are not intended to belimiting thereof.

EXAMPLE 1-1

[0167] [Preparation of Mixture No. 1]

[0168] 19.48 g (152.0 mmol) of phthalonitrile, 1.03 g (8.00 mmol) of2,3-dicyanopyridine, 14.97 g (44.00 mmol) of tetra-n-butyl o-titanate,4.80 g (80.00 mmol) of urea, and 24.48 g of 1-octanol were mixed andheated with stirring at 150 to 161° C. in a stream of nitrogen for 6hours. Thereafter, the above mixture was cooled to room temperature, andfurther stirred under reflux for 30 minutes, with 80 ml of methanolbeing added thereto.

[0169] After cooled to room temperature, the resultant crystalsseparated by filtration were successively washed with toluene, methanoland water, and dried with the application of heat under reducedpressure, whereby 19.38 q of a mixture of titanyltetraazaporphyrincompounds (mixture No. 1) in the form of a blue powder was obtained inan 84.0% yield.

[0170] The results of the elemental analysis of the thus obtainedmixture No. 1 were as follows: $\begin{matrix}\quad & {\% \quad C} & {\% \quad H} & {\% \quad N} \\{Found} & 66.74 & 2.64 & 19.45\end{matrix}$

[0171] To confirm the reproducibility of the preparation method of themixture of titanyltetraazaporphyrin compounds, the procedure forpreparation of the mixture No. 1 was repeated 10 times in the samemanner as mentioned above. According to the results of elementalanalysis of the obtained mixtures, the scattering of the found values(%) of C, H and N was within 3%, It was thus confirmed that the mixtureof titanyltetraazaporphyrin compounds of the present invention wasproduced by the method of the present invention with highreproducibility.

[0172] The X-ray diffraction spectrum of the mixture oftitanyltetraazaporphyrin compounds (mixture No. 1) in the form of apowder was measured under the following conditions: X-ray tube: Cu(wavelength: 1.54 Å) Voltage: 50 kV Current: 30 mA Scanning speed: 2deg/min. Scanning scope: 3 to 40 deg. Time constant: 2 sec

[0173]FIG. 1 is an X-ray diffraction spectrum of the mixture No. 1obtained in Example 1-1. As shown in FIG. 1, the strongest peak appearsat a Bragg angle (2θ) of 26.2%.

[0174] The mass spectrometric analysis of the mixture oftitanyltetraazaporphyrin compounds (mixture No. 1) was carried out underthe following conditions:

[0175] (LC/MC Apparatus)

[0176] Manufacturer: JEOL

[0177] Model: Mass Analyzer “MS700”

[0178] (Measuring Conditions)

[0179] Ionization: Electrospray ionization (ESI) +ion mode

[0180] Flow rate: 25 μL/min

[0181] Injection mode: Infusion

[0182] Ring voltage: 80 V

[0183] Skimmer voltage: 0 V For preparation of a sample to be subjectedto the mass spectrometric analysis, the mixture No. 1 was dissolved informic acid to prepare a solution, and the thus prepared solution wasdiluted with a 50% aqueous solution of formic acid so that theconcentration of the mixture No. 1 was adjusted to 50 ppm.

[0184] The result of the mass spectrometric analysis of the mixture oftitanyltetraazaporphyrin compounds (mixture No. 1) is shown in FIG. 10.The fragment peaks {circle over (1)} to {circle over (5)} in FIG. 10correspond to the molecular weights of compounds as shown below: {circleover (1)} C₃₂H₁₆N₈OTi: 576.42 m/z {circle over (2)} C₃₁H₁₅N₉OTi: 577.41m/z {circle over (3)} C₃₀H₁₄N₁₀OTi: 578.39 m/z {circle over (4)}C₂₉H₁₃N₁₁OTi: 579.38 m/z {circle over (5)} C₂₈H₁₂N₁₂OTi: 580.37 m/z

[0185] Namely, it is confirmed that there are the following fivetitanyltetraazaporphyrin compounds {circle over (1)} to {circle over(5)} in the mixture:

[0186] A titanyltetraazaporphyrin compound {circle over (1)} of formula(1) in which A, B, C and D are each an unsubstituted benzene ring. Themolecular weight is about 576 m/z.

[0187] A titanyltetraazaporphyrin compound {circle over (2)} of formula(1) in which three of A, B, C and D are each an unsubstituted benzenering, and the rest thereof is an unsubstituted pyridine ring. Themolecular weight is about 577 m/z.

[0188] A titanyltetraazaporphyrin compound {circle over (3)} of formula(1) in which two of A, B, C and D are each an unsubstituted benzenering, and the rest thereof are each an unsubstituted pyridine ring. Themolecular weight is about 578 m/z.

[0189] A titanyltetraazaporphyrin compound {circle over (4)} of formula(1) in which one of A, B, C or D is an unsubstituted benzene ring, andthe rest thereof are each an unsubstituted pyridine ring. The molecularweight is about 579 m/z.

[0190] A titanyltetraazaporphyrin compound {circle over (5)} of formula(1) in which A , B, C and D are each an unsubstituted pyridine ring. Themolecular weight is about 580 m/z.

EXAMPLES 1-2 to 1-7

[0191] [Preparation of Mixtures Nos. 2 to 7]

[0192] The procedure for preparation of the mixture No. 1 in Example 1-1was repeated except that the mixing ratio of phthalonitrile to2,3-dicyanopyridine in Example 1-1 was changed as shown in TABLE 1.Thus, mixtures of titanyltetraazaporphyrin compounds (mixtures Nos. 2 to7) according to the present invention were obtained.

[0193] TABLE 1 also shows the yield, and TABLE 2 shows the results ofelemental analysis and the strongest diffraction peak in terms of theBragg angle (2θ) in the X-ray diffraction spectrum of each mixture.TABLE 1 Molar Ratio of Mixture Phthalonitrile to No. 2,3-dicyanopyridineYield (%) 1-1 1 19:1 84.0 1-2 2 399:1  84.0 1-3 3 39:1 84.3 1-4 4 15:185.0 1-5 5 11:1 83.3 1-6 6  7:1 83.7 1-7 7  1:1 69.2

[0194] TABLE 2 Elemental Analysis Peak in X-ray Example Mixture (FoundValue) Diffraction No. No. % C % H % N Spectrum (°) 1-1 1 66.74 2.6419.45 26.2 1-2 2 66.80 2.69 19.06 27.2 1-3 3 66.53 2.70 19.13 26.1 1-4 466.74 2.64 19.55 26.2 1-5 5 66.47 2.77 19.63 26.1 1-6 6 66.40 2.69 20.0626.2 1-7 7 66.22 2.68 20.67  6.9

EXAMPLE 1-8

[0195] [Preparation of Mixture No. 8]

[0196] 80 g of concentrated sulfuric acid was cooled on an ice-waterbath with stirring. 5.00 g of the mixture of titanyltetraazaporphyrincompounds (mixture No. 1) obtained in Example 1-1 was dissolved in smallportions in the above-mentioned sulfuric acid over a period of 30minutes. The thus obtained solution was stirred for about one hour, andthereafter, added dropwise to 500 g of ice-cold water.

[0197] After stirring for 30 minutes, the resultant crystals wereseparated by filtration, and repeatedly washed with water three times.After filtration, 28.9 g of a wet cake with a solid content of 17.3 wt %was obtained. The wet cake was dried by the application of heat theretounder reduced pressure, so that a mixture of titanyltetraazaporphyrincompounds was obtained.

[0198] The X-ray diffraction spectrum of the thus obtained. mixture oftitanyltetraazaporphyrin compounds is shown in FIG. 2.

[0199] 9.7 g of deionized water and 120 g of tetrahydrofuran were addedto 17.3 g of the above obtained wet cake. The mixture was stirred atroom temperature for 6 hours. After completion of stirring, the mixturewas filtered off, and dried under reduced pressure, so that 2.72 g of amixture of titanyltetraazaporphyrin compounds (mixture No. 8) wasobtained in the form of blue crystals.

[0200]FIG. 3 is an X-ray diffraction spectrum of the mixture No. 8. Thestrongest diffraction peak appears at 27.2° in terms of the Bragg angle(2θ) in the X-ray diffraction spectrum.

[0201] TABLE 3 shows the results of elemental analysis and the strongestdiffraction peak in terms of the Bragg angle (2θ) in the X-raydiffraction spectrum of the mixture No. 8.

EXAMPLES 1-9 TO 1-14

[0202] [Preparation of Mixtures Nos. 9 to 14]

[0203] The procedure for preparation of the mixture oftitanyltetraazaporphyrin compounds (mixture No. 8) in Example 1-8 wasrepeated except that the mixture No. 1 initially employed in Example 1-8was replaced by the mixtures Nos. 2 to 7, respectively in Examples 1-9to 1-14.

[0204] Thus, mixtures of titanyltetraazaporphyrin compounds (mixturesNos. 9 to 14) according to the present invention were obtained.

[0205] TABLE 3 shows the mixture number initially employed, the resultsof elemental analysis, and the strongest diffraction peak in terms ofthe Bragg angle (2θ) in the X-ray diffraction spectrum of each mixture.TABLE 3 Initially Elemental Analysis Peak in X-ray Example MixtureEmployed (Found Value) Diffraction No. No. Mixture % C % H % N Spectrum(°) 1-8  8 1 65.71 2.57 19.58 27.2 1-9  9 2 66.46 2.61 19.19 27.2 1-1010 3 65.79 2.54 19.45 27.3 1-11 11 4 65.81 2.59 19.58 27.3 1-12 12 565.42 2.59 19.70 27.3 1-13 13 6 65.05 2.50 19.98 27.2 1-14 14 7 64.982.50 20.10  6.9

EXAMPLE 1-15

[0206] [Preparation of Mixture No. 15]

[0207] The wet cake obtained in Example 1-8 was dried with theapplication of heat thereto under reduced pressure.

[0208] With the addition of 50 ml of tetrahydrofuran to 1.00 g ofcrystals thus obtained, the mixture was stirred under reflux for 6hours. The mixture was cooled to room temperature, and filtered off.

[0209] The resultant residue was dried with the application of heatthereto under reduced pressure, whereby 0.97 g of a mixture oftitanyltetraazaporphyrin compounds (mixture No. 15) was obtained in theform of a blue powder.

[0210]FIG. 4 is an X-ray diffraction spectrum of the mixture No. 15.

[0211] The results of elemental analysis, and the strongest diffractionpeak in terms of the Bragg angle (2θ) in the X-ray diffraction spectrumof the mixture No. 15 are shown in TABLE 4.

EXAMPLES 1-16 TO 1-18

[0212] [Preparation of Mixtures Nos. 16 to 18]

[0213] The procedure for preparation of the mixture oftitanyltetraazaporphyrin compounds (mixture No. 15) in Example 1-15 wasrepeated except that the mixture No. 1 initially employed in Example1-15 was replaced by the mixtures Nos. 2, 3 and 6, respectively inExamples 1-16, 1-17 and 1-18.

[0214] Thus, mixtures of titanyltetraazaporphyrin compounds (mixturesNos. 16 to 18) according to the present invention were obtained.

[0215] TABLE 4 shows the mixture number initially employed, the resultsof elemental analysis, and the strongest diffraction peak in terms ofthe Bragg angle (2θ) in the X-ray diffraction spectrum of each mixture.

[0216]FIG. 5 is an X-ray diffraction spectrum of the mixture No. 16prepared in Example 1-16. TABLE 4 Initially Elemental Analysis Peak inX-ray Example Mixture Employed (Found Value) Diffraction No. No. Mixture% C % H % N Spectrum (°) 1-15 15 1 65.73 2.59 19.61 26.2 1-16 16 2 66.292.60 19.23 28.5 1-17 17 3 65.81 2.58 19.39 26.1 1-18 18 6 65.85 2.6620.02 26.2

EXAMPLE 1-19

[0217] [Preparation of Mixture No. 19]

[0218] 30 g of concentrated sulfuric acid was cooled on an ice-waterbath with stirring. 0.191 g (0.33 mmol) of the mixture oftitanyltetraazaporphyrin compounds (mixture No. 7) obtained in Example1-7 was mixed with 1.71 g (0.33×9 mmol) of titanyl phthalocyanine. Thethus obtained mixture was dissolved in small portions in theabove-metioned sulfuric acid over a period of 30 minutes. The thusobtained solution was stirred for 1.5 hours, and thereafter, addeddropwise to 190 g of ice-cold water.

[0219] After stirring for 30 minutes, the reaction mixture was separatedby filtration, and washed with water, whereby 12.7 g of a wet cake wasobtained.

[0220] Thereafter, 3.3 g of deionized water and 40 g of tetrahydrofuranwere added to 6.7 g of the above obtained wet cake. The mixture wasstirred at room temperature for 6 hours. After completion of stirring,the reaction product was separated by filtration, and dried underreduced pressure, so that 0.94 g of a mixture oftitanyltetraazaporphyrin compounds (mixture No. 19) was obtained in theform of blue crystals.

[0221]FIG. 6 is an X-ray diffraction spectrum of the mixture No. 19. Thestrongest diffraction peak appears at 27.2° in terms of the Bragg angle(2θ) in the X-ray diffraction spectrum.

COMPARATIVE EXAMPLE 1-1

[0222] [Preparation of Comparative Compound No. 1]

[0223] The procedure for preparation of the mixture No. 1 (mixture oftitanyltetraazaporphyrin compounds) in Example 1-l was repeated exceptthat 152.0 mmol of phthalonitrile used in Example 1-1 was replaced by152.0 mmol of 2,3-dicyanopyridine. Thus, atitanyltetrapyridotetraazaporphyrin (comparative compound No. 1)represented by the following formula (W) was obtained.

[0224] The mass spectrometric analysis of the comparative compound No. 1was carried out under the same conditions as in Example 1-1.

[0225] The result of the mass spectrometric analysis of the comparativecompound No. 1 is shown in FIG. 11. The fragment peak {circle over (1)}in FIG. 11 corresponds to the molecular weight of the followingcompound:

C₂₈H₁₂N₁₂OTi: 580.37 m/z  {circle over (2)}

[0226] It is thus confirmed that the comparative compound No. 1 is madeof a single substance.

COMPARATIVE EXAMPLE 1-2

[0227] [Preparation of Comparative Compound No. 2]

[0228] 55 g of concentrated sulfuric acid was cooled on an ice-waterbath with stirring. 0.174 g (0.3 mmol) of thetitanyltetrapyridotetraazaporphyrin (comparative compound No. 1)obtained in Comparative Example 1-1 was mixed with 3.29 g (0.3×19 mmol)of titanyl phthalocyanine. The thus obtained mixture was dissolved insmall portions in the above-mentioned sulfuric acid over a period of 30minutes. The thus obtained solution was stirred for 1.5 hours, andthereafter, added dropwise to 350 g of ice-cold water.

[0229] After stirring for 30 minutes, the reaction mixture was separatedby filtration, and washed with water, whereby 24.0 g of a wet cake wasobtained.

[0230] Thereafter, 3.07 g of deionized water and 40 g of tetrahydrofuranwere added to 6.93 g of the above obtained wet cake. The mixture wasstirred at room temperature for 6 hours. After completion of stirring,the reaction product was separated by filtration, and dried underreduced pressure, so that 0.96 g of a mixture oftitanyltetrapyridotetraazaporphyrin and titanyl phthalocyanine(comparative compound No. 2) was obtained in the form of blue crystals.

COMPARATIVE EXAMPLE 1-3

[0231] [Preparation of comparative compound No. 3]

[0232] In accordance with the method described in Example 16 of JapanesePatent Publication 3-27111, a mixture of a plurality of coppertetraazaporphyrin compounds was prepared.

[0233] To be more specific, a mixture of 0.84 g (5.0 mmol) ofpyridine-3,4-dicarboxylic acid, 14.07 g (95.0 mmol) of phthalicanhydride, 24.02 g (400 mmol) of urea, 2.48 g (25 mmol) of cuprouschloride, 0.04 g of ammonium molybdate-4hydrate, and 80 g oftrichlorobenzene was stirred at 181-182° C. in a stream of nitrogen for15 hours.

[0234] After the reaction mixture was allowed to stand at roomtemperature, the reaction mixture was stirred under reflux for 30minutes with the addition of 80 ml of methanol, and thereafter cooled toroom temperature.

[0235] The resultant crystals separated by filtration were. successivelywashed with toluene, methanol, a 3% aqueous solution of sodiumhydroxide, water, 1% hydrochloric acid, and water, and dried at 100° C.under reduced pressure for 2 days, thereby obtaining a blue powder. Theblue powder thus obtained was washed with dioxane in a Soxhlet apparatusfor 2 days, and thereafter, dried at 100° C. under reduced pressure for2 days. Thus, 12.51 g of a mixture of a plurality of coppertetraazaporphyrin compounds (comparative compound No. 3) was obtained inthe form of a blue powder.

[0236]FIG. 9 is an X-ray diffraction spectrum of the comparativecompound No. 3.

EXAMPLE 2-1

[0237] [Fabrication of Layered Phatoconductor]

[0238] (Formation of Intermediate Layer)

[0239] A mixture of the following components was put into a ball milland subjected to ball milling for 48 hours using alumina balls with adiameter of 10 mm so that a coating liquid for intermediate layer wasprepared. Parts by Weight Oil-free alkyd resin 1.5 (Trademark “BeckoliteM6401” made by Dainippon Ink & Chemicals, Incorporated) Melamine resin(Trademark “Super 1 Beckamine G-821” made by Dainippon Ink & Chemicals,Incorporated) Titanium dioxide (Trademark 5 “Tipaque CR-EL” made byIshihara Sangyo Kaisha, Ltd.) 2-butanone 22.5

[0240] The thus prepared intermediate layer coating liquid was coated onan aluminum plate serving as an electroconductive support, and dried at130° C. for 20 minutes. Thus, an intermediate layer with a thickness ofabout 4 μm was formed on the aluminum plate.

[0241] (Formation of Charge Generation Layer)

[0242] 3 parts by weight of the mixture of titanyltetraazaporphyrincompounds (mixture No. 1) prepared in Example 1-1, serving as a chargegeneration material, 2 parts by weight of a commercially availablepolyvinyl butyral resin (Trademark “BM-S”, made by Sekisui Chemical Co.,Ltd.), and 495 parts by weight of tetrahydrofuran were mixed anddispersed, and the mixture was subjected to ball milling in a ball millusing 2-mm diameter PSZ balls for 3 hours.

[0243] Thus, a coating liquid for charge generation layer was prepared.

[0244] The thus prepared charge generation layer coating liquid wascoated on the above prepared intermediate layer, and dried at 100° C.for 20 minutes. Thus, a charge generation layer with a thickness ofabout 0.3 μm was provided on the intermediate layer.

[0245] (Formation of Charge Transport Layer)

[0246] A mixture of 7 parts by weight of a charge transport materialrepresented by formula (V) shown below, 10 parts by weight of acommercially available polycarbonate resin (Trademark “PCX-5” made byTeijin Chemicals Ltd.), and 0.0002 parts by weight of a commerciallyavailable silicone oil (Trademark “KFS0”, made by Shin-Etsu ChemicalCo., Ltd.) was dissolved in 83 parts by weight of dichloromethane, sothat a coating liquid for charge transport layer was prepared.

[0247] The thus prepared charge transport layer coating liquid wascoated on the above prepared charge generation layer, and then dried at110° C. for 20 minutes, so that a charge transport layer with athickness of about 28 μm was provided on the charge generation layer.

[0248] Thus, an electrophotographic photoconductor No. 1 according tothe present invention was fabricated.

[0249] The electrostatic characteristics of the thus fabricatedphotoconductor No. 1 were evaluated using a commercially availableelectrostatic copying sheet testing apparatus “Eaper Analyzer ModelEPA-8100” (Trademark), made by Kawaguchi Electro Works Co., Ltd. Theevaluation was carried out in a dynamic mode (at a rotational speed of1000 rpm).

[0250] The electrophotographic photoconductor No. 1 according to thepresent invention was negatively charged in the dark under applicationof −6 kV for 20 seconds. Then, the photoconductor was allowed to standin the dark for 20 seconds without applying any charge thereto, and thesurface potential Vo (V) of the photoconductor was measured.

[0251] When the surface potential of the photoconductor No. 1 reached−800 V, the photoconductor was illuminated by white light of a halogenlamp in such a manner that the illuminance on the illuminated surface ofthe photoconductor was 5.3 lux. The exposure Ew_(½) (lux·sec) requiredto reduce the surface potential (−800 V) to ½ the surface potential(−400 V) was measured.

[0252] Using the same electrostatic copying sheet testing apparatus asmentioned above, the photoconductor No. 1 was illuminated bymonochromatic light of 780 nm in such a manner that the intensity oflight on the illuminated surface of the photoconductor was 1 μW/cm². Theexposure Em_(½) (μJ/cm²) required to reduce the surface potential (−800V) to ½ the surface potential (−400 V) was measured for evaluating thesensitivity with respect to the wave range of the LD, that is, the nearinfrared region.

[0253] The results are shown in TABLE 5.

[0254] Furthermore, the electrophotographic photoconductors werefabricated in the same manner as mentioned above, using as the chargegeneration materials the ten kinds of mixtures oftitanyltetraazaporphyrin compounds which had been prepared in Example1-1 in order to confirm the reproducibility of the preparation method.

[0255] When the electrostatic characteristics of the thus fabricatedelectrophotographic photoconductors were evaluated in the same manner asmentioned above, it was confirmed that the reproducibility was excellentwith respect to the electrophotographic properties.

EXAMPLES 2-2 TO 2-19

[0256] The procedure for fabrication of the electrophotographicphotoconductor No. 1 according to the present invention in Example 2-1was repeated except that the mixture No. 1 serving as the chargegeneration material employed in Example 2-1 was replaced by the mixturesNo. 2 to No. 19.

[0257] Thus, electrophotographic photoconductors No. 2 to No. 19according to the present invention were fabricated.

[0258] The electrostatic characteristics of those photoconductors wereevaluated in the same manner as in Example 2-1. The results are shown inTABLE 5.

EXAMPLE 2-20

[0259] [Fabrication of Layered Photoconductor]

[0260] (Formation of Charge Transport Layer)

[0261] The same charge transport layer coating liquid as employed inExample 2-1 was coated on an aluminum-deposited polyester film by bladecoating, and dried at 120° C. for 10 minutes, so that a charge transportlayer with a thickness of about 20 μm was formed on thealuminum-deposited polyester film.

[0262] (Formation of Charge Generation Layer)

[0263] A mixture of 13.5 parts by weight of the mixture No. 15 (amixture of titanyltetraazaporphyrin compounds prepared in Example 1-15),5.4 parts by weight of a commercially available polyvinyl butyral resin(Trademark “XYHL”, made by Union Carbide Japan K.K.), 680 parts byweight of tetrahydrofuran, and 1020 parts by weight of ethyl cellosolvewas pulverized and dispersed in a ball mill. With the addition of 1700parts by weight of ethyl cellosolve to the above mixture, a coatingliquid for charge generation layer was prepared.

[0264] The charge generation layer coating liquid was coated on theabove prepared charge transport layer by spray coating, and dried at100° C. for 10 minutes. Thus, a charge generation layer with a thicknessof about 0.2 μm was formed on the charge transport layer.

[0265] (Formation of Protective Layer)

[0266] A commercially available polyamide resin (Trademark “CM-8000”made by Toray Industries, Inc.) was dissolved in a mixed solvent ofmethanol and n-butanol, so that a coating liquid for protective layerwas prepared.

[0267] The protective layer coating liquid was coated on the aboveprepared charge generation layer by spray coating, and dried at 120° C.for 30 minutes, so that a protective layer with a thickness of about 0.5μm was formed on the charge generation layer.

[0268] Thus, an electrophotographic photoconductor No. 20 according tothe present invention was fabricated.

[0269] The electrostatic characteristics of the photoconductor No. 20were evaluated in the same manner as in Example 2-1 except that thephotoconductor was positively charged in the dark under application of+6 kV.

[0270] The results are shown in TABLE 5.

EXAMPLE 2-21

[0271] [Fabrication of Single-layered Photoconductor]

[0272] 158 parts by weight of methyl ethyl ketone were added to one partby weight of the mixture No. 12 (mixture of titanyltetraazaporphyrincompounds prepared in Example 1-12), and the thus obtained mixture wassubjected to ball milling for 24 hours using alumina balls with adiameter of 5 mm.

[0273] To this mixture, 12 parts by weight of the electron transportmaterial of the following formula (S) and 18 parts by weight of acommercially available polyester resin (Trademark “Polyester Adhesive49000” made by Du Pont Kabushiki Kaisha) were added. The thus preparedmixture was further dispersed, so that a coating liquid forphotoconductive layer was prepared.

[0274] The photoconductive layer coating liquid was coated on analuminum-deposited polyester film by a doctor blade, and dried at 100°C. for 30 minutes, whereby a photoconductive layer with a thickness ofabout 15 μm was formed on the aluminum-deposited polyester film.

[0275] Thus, an electrophotographic photoconductor No. 21 according tothe present invention was fabricated.

[0276] The electrostatic characteristics of the photoconductor No. 21were evaluated in the same manner as in Example 2-1 except that thephotoconductor was positively charged in the dark under application of+6 kV.

[0277] The results are shown in TABLE 5.

COMPARATIVE EXAMPLE 2-1

[0278] [Fabrication of Comparative Layered Photoconductor]

[0279] The procedure for fabrication of the electrophotographicphotoconductor No. 1 according to the present invention in Example 2-1was repeated except that the mixture No. 1 serving as the chargegeneration material in Example 2-1 was replaced by the comparativecompound No. 1 prepared in Comparative Example 1-1.

[0280] Thus, a comparative electrophotographic photoconductor No. 1 wasfabricated.

[0281] The electrostatic characteristics of the comparativephotoconductor No. 1 were evaluated in the same manner as in Example1-1. The results are shown in TABLE 5.

COMPARATIVE EXAMPLE 2-2

[0282] [Fabrication of Comparative Layered Photoconductor]

[0283] The procedure for fabrication of the electraphotographicphotoconductor No. 1 according to the present invention in Example 2-1was repeated except that the mixture No. 1 serving as the chargegeneration material, in Example 2-1 was replaced by the comparativecompound No. 2 prepared in Comparative Example 1-2.

[0284] Thus, a comparative electrophotographic photoconductor No. 2 wasfabricated.

[0285] The electrostatic characteristics of the comparativephotoconductor No. 2 were evaluated in the same manner as in Example2-1. The results are shown in TABLE 5. TABLE 5 Em_(1/2) Photoconduc-Mixture Vo Ew_(1/2) (μJ/ tor No. No. (V) (lux · sec) cm²) Ex. 2-1  1  1−743 0.77 0.41 Ex. 2-2  2  2 −832 0.64 0.33 Ex. 2-3  3  3 −780 0.74 0.38Ex. 2-4  4  4 −734 0.76 0.39 Ex. 2-5  5  5 −838 0.84 0.47 Ex. 2-6  6  6−825 0.78 0.43 Ex. 2-7  7  7 −815 0.91 0.55 Ex. 2-8  8  8 −1034  0.190.12 Ex. 2-9  9  9 −1093  0.17 0.10 Ex. 2-10 10 10 −1134  0.17 0.10 Ex.2-11 11 11 −1024  0.21 0.14 Ex. 2-12 12 12 −996 0.21 0.16 Ex. 2-13 13 13−914 0.27 0.18 Ex. 2-14 14 14 −616 0.50 0.31 Ex. 2-15 15 15 −947 0.430.21 Ex. 2-16 16 16 −1242  0.22 0.15 Ex. 2-17 17 17 −1013  0.27 0.19 Ex.2-18 18 18 −798 0.31 0.15 Ex. 2-19 19 19 −963 0.23 0.15 Ex. 2-20 20 15+1122  0.31 0.25 Ex. 2-21 21 12 +826 0.36 0.29 Comp. ComparativeComparative −567 4.50 2.26 Ex. 2-1 Photoconduc- Compound tor No. 1 No. 1Comp. Comparative Comparative −655 2.12 1.55 Ex. 2-2 Photoconduc-Compound tor No. 2 No. 2

COMPARATIVE EXAMPLE 2-3

[0286] [Fabrication of Comparative Layered Photoconductor]

[0287] The procedure for fabrication of the electrophotographicphotoconductor No. 1 according to the present invention in Example 2-1was repeated except that the mixture No. 1 serving as the chargegeneration material in Example 2-1 was replaced by such a Y-typetitanylphthalocyanine compound that exhibited an X-ray diffractionspectrum shown in FIG. 7.

[0288] Thus, a comparative electrophotographic photoconductor No. 3 wasfabricated.

[0289] The electrostatic fatigue characteristics of the comparativephotoconductor No. 3 were evaluated using a commercially availableelectrostatic copying sheet testing apparatus “Paper Analyzer ModelEPA-9100” (Trademark), made by Kawaguchi Electro Works Co., Ltd. Theevaluation was carried out in a dynamic mode (at a rotational speed of1000 rpm).

[0290] The comparative electrophotographic photoconductor No. 3 wasnegatively charged in the dark under application of −6 kV, while exposedto white light of a halogen lamp, with the conduction current beingmaintained at about 5.6 μA, and the charging potential at −800 V. 30minutes later, the surface potential was measured. Upon measurement, thephotoconductor was again charged while exposed to light for 30 minutesin the same manner as mentioned above. Then, the surface potential wasagain measured.

[0291] The photoconductor No. 1 according to the present inventionfabricated in Example 2-1 was also subjected to the above-mentionedfatigue test to evaluate the electrostatic fatigue characteristics.

[0292]FIG. 8 shows the change in surface potential (V) of eachphotoconductor in the above-mentioned fatigue test.

[0293] As can be seen from the results shown in FIG. 8, the surfacepotential of the photoconductor No. 1 was more stable than that of thecomparative photoconductor No. 3 in the fatigue test. The mixture of aplurality of different titanyltetraazaporphyrin compounds serving as thephotoconductive material in the photoconductor is considered to beuseful to stabilize the electrostatic characteristics in the fatigueperformance.

COMPARATIVE EXAMPLE 2-4

[0294] [Fabrication of Comparative Layered Photoconductor]

[0295] The procedure for fabrication of the electrophotographicphotoconductor No. 1 according to the present invention in Example 2-1was repeated except that the mixture No. 1 serving as the chargegeneration material in Example 2-1 was replaced by the comparativecompound No. 3 prepared in Comparative Example 1-3.

[0296] Thus, a comparative electrophotographic photoconductor No. 4 wasfabricated.

[0297] The electrostatic characteristics of the comparativephotoconductor No. 4 were evaluated in the same manner as in Example2-1. As a result, the surface potential (Vo) was −585 V. In addition,there were no sensitivities to both the white light and themonochromatic light when the comparative compound No. 3 was employed inthe photoconductor.

EXAMPLE 3-1

[0298] [Fabrication of Image Forming Apparatus]

[0299] An image forming apparatus was provided with theelectrophotographic photoconductor No. 1 (fabricated in Example 2-1)according to the present invention.

[0300] Using the above-mentioned image forming apparatus, images wereproduced. The produced images were remarkably clear.

[0301] As previously explained, the mixture of a plurality of differenttitanyltetraazaporphyrin compounds according to the present invention isuseful as the organic photoconductive material for theelectrophotographic photoconductor which is employed in the high-speedcopying machine or laser printer.

[0302] The photoconductor of the present invention is superior to theconventional photoconductor because the sensitivity is excellent notonly in the visible light range, but also in the near infrared range,the charging characteristics are improved, and the fatigue propertiesare also excellent. Therefore, the photoconductor of the presentinvention is considered to be useful when employed in the high-speedcopying machine and laser printer.

[0303] Japanese Patent Application No. 10-328248 filed Nov. 18, 1998 ishereby incorporated by reference.

What is claim is:
 1. A mixture of a plurality of differenttitanyltetraazaporphyrin compounds, each of which is represented byformula (1):

wherein A, B, C and D are each independently an unsubstituted orsubstituted benzene ring or an unsubstituted or substituted pyridinering, with a substituent thereof being selected from the groupconsisting of nitro group, cyano group, a halogen atom, an alkyl grouphaving 1 to 8 carbon atoms, an alkoxyl group having 1 to 8 carbon atoms,and an aryl group.
 2. The mixture as claimed in claim 1, exhibitingpeaks at 576, 577, 578, 579 and 580 when subjected to mass spectrometricanalysis.
 3. The mixture as claimed in claim 1, comprising: (a) atitanyltetraazaporphyrin compound with said formula (1) in which A, B, Cand D are each an unsubstituted benzene ring, (b) atitanyltetraazaporphyrin compound with said formula (1) in which threeof A, B, C and D are each an unsubstituted benzene ring and the restthereof is an unsubstituted pyridine ring, (c) atitanyltetraazaporphyrin compound with said formula (1) in which two ofA, B, C and D are each an unsubstituted benzene ring and the restthereof are each an unsubstituted pyridine ring, (d) atitanyltetraazaporphyrin compound with said formula (1) in which one ofA, B, C or D is an unsubstituted benzene ring, and the rest thereof areeach an unsubstituted pyridine ring, and (e) a titanyltetraazaporphyrincompound with said formula (1) in which A, B, C and D are each anunsubstituted pyridine ring.
 4. The mixture as claimed in claim 1,exhibiting at least one of diffraction peaks at 6.9°, 26.2°, 27.2°and28.5° in terms of a Bragg angle of 2θ±0.2° in an X-ray diffractionspectrum using a Cu-Kα ray with a wavelength of 1.54 Å.
 5. The mixtureas claimed in claim 1, wherein said mixture of saidtitanyltetraazaporphyrin compounds is produced by allowingphthalonitrile, dicyanopyridine, and a titanium compound to react.
 6. Amethod of producing at least one mixture of a plurality of differenttitanyltetraazaporphyrin compounds, each of whichtitanyltetraazaporphyrin compounds is represented by formula (1):

wherein a, B, C and D are each independently an unsubstituted orsubstituted benzene ring or an unsubstituted or substituted pyridinering, with a substituent thereof being selected from the groupconsisting of nitro group, cyano group, a halogen atom, an alkyl grouphaving 1 to 8 carbon atoms, an alkoxyl group having 1 to 8 carbon atoms,and an aryl group, comprising the step of allowing phthalonitrile,dicyanopyridine and a titanium compound to react.
 7. The method asclaimed in claim 6, wherein at least two of said mixtures which aredifferent are produced and mixed, each of said different mixtures beingproduced by mixing said phthalonitrile and said dicyanopyridine at adifferent mixing ratio.
 8. The method as claimed in claim 6, furthercomprising the step of adding a phthalocyanine pigment to said mixturewhen said phthalonitrile and said dicyanopyridine are mixed.
 9. Themethod as claimed in claim 7, further comprising the step of adding aphthalocyanine pigment to each of said different mixtures when saidphthalonitrile and said dicyanopyridine are mixed.
 10. The method asclaimed in claim 6, further comprising the step of subjecting saidmixture to crystal modification treatment.
 11. An electrophotographicphotoconductor which comprises an electroconductive support and aphotoconductive layer formed thereon comprising a mixture of a pluralityof different titanyltetraazaporphyrin compounds, each of which isrepresented by formula (1):

wherein A, B, C and D are each independently an unsubstituted orsubstituted benzene ring or an unsubstituted or substituted pyridinering, with a substituent thereof being selected from the groupconsisting of nitro group, cyano group, a halogen atom, an alkyl grouphaving 1 to 8 carbon atoms, an alkoxyl group having 1 to 8 carbon atoms,and an aryl group.
 12. The photoconductor as claimed in claim 11,wherein said mixture exhibits peaks at 576, 577, 578, 579 and 580 whensaid mixture is subjected to mass spectrometric analysis.
 13. Thephotoconductor as claimed in claim 11, wherein said mixture comprises:(a) a titanyltetraazaporphyrin compound with said formula (1) in whichA, B, C and D are each an unsubstituted benzene ring, (b) atitanyltetraazaporphyrin compound with said formula (1) in which threeof A, B, C and D are each an unsubstituted benzene ring and the restthereof is an unsubstituted pyridine ring, (c) atitanyltetraazaporphyrin compound with said formula (1) in which two ofA, B, C and D are each an unsubstituted benzene ring and the restthereof are each an unsubstituted pyridine ring, (d) atitanyltetraazaporphyrin compound with said formula (1) in which one ofA, B, C or D is an unsubstituted benzene ring, and the rest thereof areeach an unsubstituted pyridine ring, and (e) a titanyltetraazaporphyrincompound with said formula (1) in which A, B, C and D are each anunsubstituted pyridine ring.
 14. The photoconductor as claimed in claim11, wherein said mixture exhibits at least one of diffraction peaks at6.9°, 26.2°, 27.2° and 28.5° in terms of a Bragg angle of 2θ±0.2° in anX-ray diffraction spectrum using a Cu-Kα ray with a wavelength of 1.54Å.
 15. The photoconductor as claimed in claim 11, wherein said mixtureof said titanyltetraazaporphyrin compounds is produced by allowingphthalonitrile, dicyanopyridine, and a titanium compound to react. 16.An image forming apparatus comprising an electrophotographicphotoconductor which comprises an electroconductive support and aphotoconductive layer formed thereon comprising a mixture of a pluralityof different titanyltetraazaporphyrin compounds, each of which isrepresented by formula (1):

wherein A, B, C and D are each independently an unsubstituted orsubstituted benzene ring or an unsubstituted or substituted pyridinering, with a substituent thereof being selected from the groupconsisting of nitro group, cyano group, a halogen atom, an alkyl grouphaving 1 to 8 carbon atoms, an alkoxyl group having 1 to 8 carbon atoms, and an aryl group.